1. Field of the Invention
This invention relates to a string for a sports racket, more particularly to a string having a toothed core and a sheath layer molded over the toothed core.
2. Description of the Related Art
A known type of conventional racket string is formed from a plurality of core filaments which are twisted together upon passing through an impregnating container carrying a thermoplastic resin therein for impregnating the filaments so as to increase the elasticity of the string. This type of string generally has poor wear-resistance. When the string is used in a racket, high impact and friction induced upon hitting a ball would result in severe wearing of the string.
Another conventional string is formed from a plurality of core filaments sheathed by a moisture-cured polyurethane which provides hardness to increase the wear-resistance of the string. However, this type of string has poor elasticity. Thus, reactive force produced in the string upon impact may injure the user""s hand.
Therefore, it is an object of the present invention to provide a string for a sports racket that has a structure capable of providing good wear-resistance and elasticity.
Accordingly, a string for a racket of the present invention comprises: a base core formed from at least a first filament; an intermediate layer formed from a plurality of second filaments and enclosing the base core; and a first sheath layer enclosing the intermediate layer. At least one of the first filament and the second filaments has a molded structure which includes a toothed core that is made of a first plastic material and that has a toothed outer surface, and a second sheath layer that is made of a second plastic material and that is molded over the toothed core so as to be bonded to the toothed outer surface. The first plastic material has a hardness and a wear-resistance less than those of the second plastic material.